The Development Of ChildrenChapter 2

The Human Heritage: Genes and the Environment

Bottom Line 1 - Terms to know in Ch

2• Mitosis and Meiosis• Chromosomes: Males have XY and Females have XX chromosomes

• Genes• DNA• Dominant and Recessive Genes

Bottom Line 2Concepts to know in

Ch 2• Genetics + Environment = Characteristics Sex-linked characteristics

• Gene-environment interaction - bunnies!

• Genes and behavior - family, twin and adoption studies

• Causes of Genetic Abnormalities (Down Syndrome, PKU, Sickle Cell anemia, Klinefelter Syndrome)

Down Syndrome • Cause: 3 (vs. 2) copies of chromosome 21

• Traits: Mentally/physically retarded and distinctive physical characteristics

• Incidence: 1:1000 births

• Outlook: Special education markedly improve intellectual, social, physical and creative functioning

Phenylketonuria (PKU)• Cause: Defective recessive gene

resulting in retarded development of prefrontal cortex

• Traits: Severe retardation• Incidence: 1:10,000 • Outlook: Feeding PKU infants a diet avoiding milk, eggs, bread, fish reduces the severity of mental retardation

Sickle-Cell Anemia• Cause: Recessive gene (victims are homozygous, but heterozygous subjects are also mildly affected)

• Traits: Abnormal blood cells cause circulatory problems (e.g., heart enlargement) and severe anemia

• Incidence: 8-9% of U.S. blacks

• Outlook: Crippling, but treatable with medication

Klinefelter Syndrome• Cause: Extra X chromosome

(i.e., XXY)• Traits: Males fail to develop

secondary sex characteristics (e.g., facial hair, voice change), are sterile, and most have speech and language problems

• Incidence: 1:900 males• Outlook: May be treatable with

testosterone replacement therapy

Survival Strategies: Culture• Cultural artifacts, such

as tools and clothing, greatly extend the range of environments in which human beings can reproduce and thrive

• Cultural knowledge, such as the creation of “hazard prevention strategies,” serves to protect and support children to enable them to mature and reproduce